🩸 THE CIRCULATORY SYSTEM
PAGE 1 OF 5 · THE MIGHTY PUMP
LUB-DUB
YOUR HEART NEVER CLOCKS OUT
The heart is a muscular organ about the size of your fist. It squeeze-releases about 100,000 times a day, pushing blood into thick-walled arteries. The double beat you hear is valves snapping shut after each push. This pump started before you took your first breath and plans to outlast your homework — if you treat it well.
⚡ DID YOU KNOW?
If you laid every blood vessel end to end, adults could stretch roughly 100,000 km — enough to wrap around Earth more than twice.
BEAT!
FOUR CHAMBERS
💓 Two atria receive blood.
💪 Two ventricles shoot it onward.
💪 Two ventricles shoot it onward.
MILES OF TUBING
🌍 Arteries split into tiny branches.
🔄 Veins merge as blood heads home.
🔄 Veins merge as blood heads home.